Question

The valence shell of calcium contains ______.
(A) 2 electrons
(B) 4 electrons
(C) 6 electrons
(D) 8 electrons

Answer 1

Hint: The number of electrons present in the valence shell of an electron depends upon the atomic number of an element and the electron distribution or configuration into the orbitals.
Valence shell is the last or outermost shell of an atom which denotes the valency of the neutral atom.

Complete answer:
Let us know about the valence shell and electronic configuration before moving towards the specified element;
Valence shell-
The outermost shell or the orbit which has valence electrons or outer electrons is known as valence shell. The valence electrons are the ones which can be removed or gained by an element to stabilise itself in nature.
Electronic configuration-
The atomic number is the basic requirement to determine the electronic configuration of the element and thus, the valence electrons. The general electronic configuration for the element stated by Bohr is given as 2, 8, 8, 18, 18, 32, 32.
Illustration-
Now we know that calcium is the element with the atomic number as 20. Thus, the electronic configuration as stated by Bohr is given as 2, 8, 8, 2.
By the above information, we can see that the last shell of calcium atom consists of 2 electrons. Thus, the valence electrons in the calcium atom is 2.

Therefore, option (A) is correct.

Note:
Do note that the valence electrons and valency can be different for an atom as, when valence electrons are 3; valency is also 3 but when valence electrons are 6; valency is 2. This is because the atom tries for the stability and completion of the octet at any cost.